Saturday, November 20, 2010

Modus ponens

MODUS PONENS: Latin MODUS "standard, measure" is from the Indo-European root MED- "to take appropriate measures." The second word, PONENS, is the present participle of Latin PONERE "to put." (See more under COMPONENT.) In logic, MODUS PONENS is a standard form of argumentation in which you "put down" the antecedent of an if-then statement and conclude the occurrence of the consequence of that if-then statement.

In classical logic, modus ponendo ponens (Latin for the way that affirms by affirming; often abbreviated to MP or modus ponens) is a valid, simple argument form sometimes referred to as affirming the antecedent or the law of detachment. It is closely related to another valid form of argument, modus tollens.

Modus ponens is a very common rule of inference, and takes the following form:

1. If P, then Q.
2. P.
3. Therefore, Q.

Modus ponens is related to modus tollens. They both have a premise that is a conditional statement. The most important difference lies in the negation of the last two lines.